Optical Square - (OS-01)
Consists of Brass / suitable metal hollow box having open face about 6 x 3 cms. and closed face about 2 x 3 cm. and deep about 4cm to 5cm. provided with a brass handle about 8cm. in length. Two mirrors fixed at an angle of 45 degree to the inclined sides of the box. Circular type made up of brass & fitted with double reflecting mirror right & left to 90, in case.